MD Helicopters 369-500, Maintenance Instructions Manual

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CSP-HMI-3
MD Helicopters, Inc
.
MAINTENANCE MANUAL
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Neither this document nor any part hereof may be reproduced or transferred to
other documents or used or disclosed to others for manufacturing or any other
purpose except as specifically authorized in writing by MD Helicopters, Inc.
Copyright
©
1999 − 2016 by MD Helicopters, Inc.
INTERCOMMUNICATION SYSTEM (KING)
DESCRIPTION AND OPERATION
1. Description and Operation
The intercommunication system (ICS) provides
an intercommunication capability between
pilot, copilot and passenger stations. A KMA
24H audio control panel installed in the
instrument panel allows 1) selection, control,
and monitoring of voice communication, 2)
monitoring of audio signals from communica­
tions transceivers (COMM), and 3) monitoring
of the following receivers: vhf navigation
(NAV), distance measuring equipment (DME),
marker (MKR), and automatic direction finder
(ADF). Received radio signals may be moni­
tored at all intercom stations. In addition, the
pilot or copilot may select the COMM trans­
ceivers for voice transmission to other aircraft
or ground stations.
The KMA 24H has a pushbutton audio selector
panel, five-station intercom, and separate
speaker and headphone isolation amplifiers.
Dual KMA 24H installations in some helicop­
ters provide added flexibility, allowing the pilot
or copilot or a passenger to speak on different
transmitters simultaneously while providing
pilot priority if the same transmitter is keyed
by both operators at the same time.
The separate isolation amplifiers maintain
constant, noise-free volume levels, even when
several receivers are monitored at once. The
amplifiers are powered by separate, indepen­
dent supply sources. There are two identical
headphone amplifiers, the primary (serving
the pilot) and the secondary (serving the crew
and intercom stations). This feature enables
the pilot and/or copilot to isolate out of the
intercom loop if desired. Each headphone
amplifier can drive up to six 500 ohm head­
sets.
The KMA 24H contains a summing amplifier
to combine received audio with the pilot's
microphone for installations where a voice
recorder is necessary. This amplifier output
always contains the pilot headphone audio and
hot mic audio from MIC 1 as per CAA specifi­
cation No. 11, Issue 3.
As many as five transceivers and five receivers
can be controlled by the -71 version of the
KMA 24H. As many as four transceivers and
six receivers can be controlled by the -70
version of the KMA 24H. The units also have
two un-switched inputs; these are used to
transmit the audible engine out warning
signal and the low altitude warning signal (if a
radar altimeter is installed) to the crew. Five
intercom station inputs are available, two of
which also serve as the transmit microphone
inputs. The MIC 1 and MIC 2 microphone keys
control internal relays to automatically switch
these inputs from ``intercom'' to ``transmit''. In
the event of power interruption to the KMA
24H, the relays automatically set to ``transmit''
so that use of the transceiver is not impaired.
In helicopters with the optional mode select
switch installed (Ref. Figure 2), the MIC 2
relay will not switch to ``transmit'' in the
Isolate mode (single installation only). (Ref.
Para. Modes of Operation (Helicopters with
Optional Mode Select Switch Only) below.)
In single KMA 24H installations, the pilot's
microphone (MIC 1) has priority over the
copilot's (MIC 2). In dual KMA 24H installa­
tions, the pilot's microphone has priority over
the copilot's only when both parties have
selected the same transceiver. When either the
pilot or copilot keys the microphone to trans­
mit, all other microphone inputs are muted to
ensure that the keyed microphone is the single
source of the transmitted audio. Keying a mike
mutes all receivers automatically, to eliminate
feedback. The audio inputs selected from the
pushbuttons on the KMA 24H are also muted
while the pilot or copilot is transmitting. If the
pilot and copilot should both key their micro­
phones at the same time, the pilot's micro­
phone will override the copilot's. In the
instances when a headphone output contains
1) audio selected by the pushbuttons and 2)
engine out and low altitude warnings, the TX
key will mute all audio from the headphone
output except transmit sidetone, engine out
warning, and low altitude warning. In
addition, the TX key will mute from the
speaker output all audio except engine out
warning and low altitude warning. A P.A.